Anaximander is the first philosopher whose theory of the heavens is preserved in broad outlines. According to the sources the celestial bodies are huge rings of compressed air around the earth, each visible only where it is perforated by a tubular vent through which the fire contained in it can shine. Greatest and farthest of them is the sun, next comes the moon and under them there is the ring of the stars. It is a common practice to put and answer the following questions: ‘…why he should have placed the stellar circles or rings closer to the earth than are the sun and the moon.’ ‘…why these lower rings of stellar ρ do not obscure the brighter but more distant bodies.’